No one can tell you that you've made a poor choice to go with Mesa. I've tried out quite a few brands, and Mesa was head and shoulders above everything else in terms of build quality, features, tone and power.
Myself, I have a Basis M-2000 head into a Powerhouse 4x10 and a Powerhouse 1x15, and all the venues I've played so far, I could have played without PA support (didn't do that, though, because it's a pain in the ass for the soundman

).
If you're a knob tweaker and want a killer hybrid head with separate, blendable tube and FET channels, then this head is for you. I could not find a head out there that had the features this thing has. I was considering the Ampeg SVT-4 PRO, but decided against it due to the myriad of reviews I read complaining about its reliability. Though it is rated at 1200 Watts, I'd say that that's wishful thinking on the part of Ampeg.
I was also looking at the Genz Benz GBE1200, but after playing through the GBE600, I decided I wanted a more "tubey" sound, and the Mesa gave me exactly that, but with the potential to blend some serious low-end and punch from the FET channel. Couple that with 625 very conservative Watts, a footswitch that's worth $240 USD by itself and can select a separate high-gain channel for the tube side, and you've got a winning combination. I bought it from Tom Bowlus and have never looked back.
Flea used to played a Buster Bass 200, and before that I think he may have used the D-180, and his tone was absolutely amazing while he used Mesa (it also has to do with the fact that he was using MusicMans and Wal basses at the time; his Modulus days aren't yielding the tone I characterize Flea with, but that's just me.)
That's my $0.02. Hope it helps!